2 Statistic Questions, can use TI-83 or TI-84 to solve problems

In a preliminary study, the sample standard deviation for the duration of a particular

back pain suffered by patients was 18.0 months. How large a random sample is

needed to construct a 90% confidence interval so that an estimate can be made within

2 months of the actual duration ?

In preparing a report on the economy, we need to estimate the percentage of

businesses that plan to hire additional employees in the next 60 days. How many

randomly selected employers must we contact in order to create an esti

mate in whichwe are 98% confident, with an error of 5% ?